1. Field of the Invention
The present invention relates to a hydraulic oil flow controller for a construction machine such as a hydraulic shovel, and more particularly to a hydraulic oil flow controller for a construction machine which controls the hydraulic oil flow suitable for the attachment work of a hydraulic shovel.
2. Description of the Related Art
FIG. 6 schematically shows the entire body of a hydraulic shovel 45. The hydraulic shovel 45 comprises a lower travelling body 45, an upper swing body 47 mounted thereon so as to freely swing, a rotary boom 48 extending forward from the upper swing body 47, a rotary arm 49 attached to the end of boom 48 and a rotary bucket 51 attached to the end of the arm 49. A drilling work by using the hydraulic shovel 45 is ordinarily carried out by manipulating an operating lever arranged in an operating room by an operator. The operator manipulates the operating lever so that hydraulic oil from a hydraulic pump flows out from an operating valve in accordance with the manipulated variable or the control input of the operating lever. The hydraulic oil flowing out from the operating valve is supplied to a main actuator. When the hydraulic oil is supplied to the main actuator, the actuator is driven and the drilling work is carried out. Further, the hydraulic shovel 45 can perform such operations as breaking or crushing works by attaching attachments such as a breaker or a crusher to the end of the arm in place of the bucket 51. The breaking or crushing work is carried out by operating an operating pedal disposed at the feet of the operator in the operating room.
The relation between a distance that the operating pedal is stepped on, which will be referred to simply as a distance hereinafter, and the flow or the flow rate of hydraulic oil flowing out from the operating valve in the prior art is of this sort that the flow is zero when the operating pedal is not stepped on, the flow is increased step by step as the operating pedal is gradually stepped on and the flow becomes maximum when the operating pedal is stepped on to its maximum. Accordingly, the flow is readily determined depending on the distance from the beginning of stepping on the operating pedal until the maximum distance of the operating pedal. Therefore, the relation between the distance of the operating pedal and the flow ordinarily shows a substantially linear relation.
The flow of hydraulic oil flowing out from the operating valve in the hydraulic shovel is preset to the value of flow necessary for driving the main actuator. The flow of a small attachment such as a simplex breaker necessary for driving the actuator is extremely less than the flow necessary for driving the main actuator. Accordingly, when the actuator of the small attachment is driven in accordance with the flow necessary for driving the main actuator, the maximum flow obtained when the operating pedal is stepped on at its maximum is excessively more than that necessary for driving the actuator of the small attachment. Therefore, in order to obtain the flow necessary for driving the actuator of the small attachment, the distance that the operating pedal is stepped on is decreased and the distance further needs to be increased or decreased so that it can be properly adjusted. However, since all the distance of the operating pedal when actuating the main actuator corresponds to the maximum flow which is excessively set relative to the flow required for driving the actuator of the small attachment, a coefficient of fluctuation of the flow relative to a coefficient of fluctuation of the distance of the operating pedal is undesirably large. Therefore, the flow is undesirably greatly fluctuated only by slightly increasing or decreasing the distance of the operating pedal. Accordingly, it has been very difficult to increase or decrease the distance of the operating pedal so that the distance is suitably adjusted to obtain a flow required for driving the actuator of the small attachment and the operation efficiency of the small attachment has been inconveniently deteriorated.
The present invention is proposed to overcome the above-described problems of the prior art and it is an object of the present invention to provide a hydraulic oil flow controller for a construction machine in which the coefficient of fluctuation of flow relative to the coefficient of fluctuation of a manipulated variable can be decreased and the operation efficiency of an attachment can be improved when the attachment is operated.
A hydraulic oil controller for a construction machine comprises an operating valve 6 for supplying hydraulic oil from hydraulic pumps 1 and 2 to the actuator of an attachment, an attachment operating unit 11 for transmitting a pilot signal corresponding to a manipulated variable or a control input to the operating valve 6 and a solenoid control valve 12 for changing the flow characteristics of the pilot signal in accordance with a command from a controller 19, wherein an increase and/or decrease signal is sent to the solenoid control valve 12 through the controller 19 from a monitor device 18 so that the flow of hydraulic oil supplied to the actuator of the attachment is increased and/or decreased and the flow determined by the increase and/or decrease signal is displayed on a monitor screen.
In the hydraulic oil flow controller for a construction machine according to a first embodiment, when a signal for decreasing the flow of discharged hydraulic oil is sent to the solenoid control valve 12 through the controller 19 from the monitor device 18, the flow characteristics of the pilot signal acting on the operating valve 6, for instance, pilot pressure is decreased. The pilot pressure is decreased, so that the flow of the hydraulic oil supplied to the actuator of the attachment can be decreased in accordance with the manipulated variable or the control input of the attachment operating unit and the coefficient of fluctuation of the flow relative to the coefficient of fluctuation of the manipulated variable of the attachment operating unit is decreased. Consequently, the operation efficiency of the attachment operating unit can be improved. Further, the flow of the hydraulic oil supplied to the actuator of the attachment is increased and/or decreased, and accordingly, an optimum flow can be preset to a different kind of attachment, the unnecessary exhaust loss of the flow can be reduced, a power efficiency can be raised and energy-saving can be achieved. Still further, the flow determined by increasing and/or decreasing the flow is displayed on the monitor screen. Thus, the set flow can be visually recognized and the operation efficiency can be improved.
Further, according to the hydraulic oil flow controller for a construction in a second embodiment, an increase and/or decrease signal is transmitted to the controller 19 by an increase and/or decrease switch provided in the monitor screen on in the vicinity thereof.
In the hydraulic oil flow controller for a construction machine as described in the second embodiment, since the increase and/or decrease switch for increasing and/decreasing the flow supplied to the actuator of the attachment is provided in the monitor screen or in the vicinity of the monitor screen, the switch for increasing and/or decreasing the flow of the hydraulic oil can be operated while viewing the monitor screen. Thus, the operation efficiency of the switch can be improved and the operation efficiency of a whole device can be improved.
Still further, the hydraulic oil flow controller for a construction machine as described in a third embodiment further comprises a flow separating and combining valve 3 for selectively switching the drive of a plurality of hydraulic pumps 1 and 2 and a single hydraulic pump 2 so that a select signal from a select switch is transmitted to the controller 19 by the attachment select switch and the flow separating and combining valve 3 is switched in accordance with a command from the controller 19.
Still further, in the hydraulic oil flow controller for a construction machine as described in the third embodiment, the driving of the plural hydraulic pumps 1 and 2 and the driving of the single hydraulic pump 2 are switched, so that the discharges of the plural hydraulic pumps 1 and 2 can be ensured so as to meet the attachment.
Still further, the hydraulic oil flow controller for a construction machine as described in a fourth embodiment further comprises a change-over valve 21 for selectively switching or changing over a single-acting hydraulic circuit and a double-acting hydraulic circuit, the change-over valve 21 being switched by the attachment select switch.
Furthermore, in the hydraulic oil flow controller for a construction machine as described in the fourth embodiment, since the single-acting hydraulic circuit and the double-acting hydraulic circuit can be selectively switched by the change-over valve 21, when an attachment driven by the single-acting hydraulic circuit is mounted on the machine, the circuit is switched to the single-acting hydraulic circuit so that the hydraulic oil flowing out from the actuator of the attachment is not returned to the first operating valve 6 from the change-over valve 21 and directly returned to a tank. Therefore, back pressure is lowered so that the attachment can be smoothly driven.